Dairy Bulls Research Articles

Youngstock health: Effective disease prevention today ensuring tomorrow's profitable herd

Foreword Proactive youngstock health management is critical not only to optimise animal welfare and production efficiency and profitability, but also to minimising the environmental impact of livestock production. The morbidity and mortality rates tolerated by some producers, and at times even accepted by their vets, are often far too high. Whether it is the loss of dairy bull calves, who may have little monetary value but nevertheless contribute to both the carbon footprint and other environmental impacts of a dairy if not utilised for food production, dairy heifers with the additional loss of the best genetics in the herd or a beef suckler calf representing the only product of the cow that year, we need to do all we can to prevent death and disease. Even where calves do not die, managing sick animals is costly in treatment and labour and antibiotic use in these animals to treat, and on some farms still to prevent disease, is very likely to contribute to antimicrobial resistance. The only logical conclusion that one can come to is that if cattle units are to remain viable and produce sustainable milk and meat, we need to redouble efforts to prevent disease. Sometimes we talk of new science, while at other times we find ourselves repeating ‘the same old message’. The need for adequate colostrum management is one such case, the messages may not be new but far too many calves still fail to receive enough maternally derived antibody, making the article in this supplement on colostrum vital reading. Don't assume you, or more importantly your clients, know everything there is to know about colostrum. After ensuring calves have received initial protection via maternal derived antibody from colostrum then we need to ensure they are protected from infections as they grow, particularly respiratory diseases. Despite having had good vaccines for over 20 years, their uptake in the national herd I believe is still suboptimal, far too many calves still receive antimicrobials, and poor growth rates are common due to chronic lung damage. Ellie Button explains well in her article ‘Calf disease: an immunological perspective’ the calf's innate and acquired immunity and describes how an understanding of the calf's developing immunity can be used to enhance disease prevention. Finally, Kat Hart and colleagues discuss communication and promoting behaviour change in ‘How to engage farmers in youngstock care: a clinical forum’, something that in the past we have often forgotten. It's not good enough for vets to understand the science and turn a blind eye to poor on farm practices, or to simply tell clients what to do and walk away expecting them to do as they have been told! We often need to motivate clients towards real lasting change, and to do that we all need to communicate better. Together the three articles in this supplement are a powerful combination, the challenge is to read them and then effect valuable changes on your clients’ farms.

In vitro assessment of egg yolk-, soya bean lecithin- and liposome-based extenders for cryopreservation of dairy bull semen

The study was conducted to compare the effect of four commercially available extenders (Triladyl®- egg yolk-based; Andromed® and Bioxcell®-plant based and Optixcell®-liposome-based) on post‐thaw sperm quality and functionality variables evaluated using computer‐assisted sperm analysis and flow cytometry. A total of 30 ejaculates from five bulls were analysed. With use of Triladyl®, sperm had a greater post-thaw total motility than with use of Bioxell® and Optixcell® but there was no difference as compared with use of Andromed® with the greatest (P < 0.05) percentage of progressively motile cells. With use of Optixcell®, there was a greater (P < 0.05) percentage of sperm with an intact membrane than with use of Triladyl® and Bioxcell®, but values were similar with use of Andromed®. Acrosome damage in semen preserved with use of Optixcell® was less than with use of Bioxcell® and Andromed®. With use of Optixcell®, there was a greater percentage of viable spermatozoa with a lesser lipid disruption (P < 0.05) when compared with the other extenders. Production of peroxides was greater for sperm cryopreserved with use of Triladyl® and Optixcell® while less superoxide was produced in the samples cryopreserved with the egg yolk-based extender. Optixcell® appears to be a promising alternative to replace traditional egg yolk extenders. With use of Optixcell®, however, there were greater peroxide concentrations after thawing. With use of Andromed®, there were similar results as with use of Optixcell®, therefore, it could be an effective substitute for egg-yolk based media due to the greater proportion of highly and progressively motile spermatozoa at thawing.

Genetic and genomic analysis of long insemination interval in Israeli dairy cattle as an indicator of early abortions

One of the causes of observed low fertility is embryo loss after fertilization. Previous findings suggested that more than half of fertilizations result in embryo loss before pregnancy is detected. We proposed reinsemination between 49 and 100 d after the first insemination as an indicator trait for early abortion (EA) in dairy cattle based on the mean estrus interval of 21 d. This trait was compared with conception rate from first insemination and conception status, computed as the inverse of the number of inseminations to conception. Animal model variance components were estimated by REML, including parents and grandparents of cows with records. First-parity heritability for first insemination conception rate was 3%. In the multitrait analysis of parities 1 to 3 for putative EA, heritabilities ranged from 8.9% for first parity to 10.4% for second parity. All genetic correlations were >0.9, whereas all environmental correlations were <0.12. The variance component for the service sire effect for putative EA rate was less than half the variance component for conception rate. Thus, genetic control of the 2 traits is clearly different, and analysis of EA rate by a single-trait animal model is justified. Genetic evaluation for putative EA was computed using this model, including all first- through third-parity cows with freshening dates from January 1, 1985, through December 31, 2016, that either became pregnant on first insemination or were reinseminated between 49 and 100 d after the first insemination. All known parents and grandparents of cows with records were included in the analysis. The regression of the breeding value for non-abortion rate on the cows' birth year was 0.083%/yr. The genetic correlation between first-parity EA and conception status was 0.995. The genetic correlations between first-parity EA and milk, fat, and protein production were all negative, whereas the genetic correlation between EA and herd life was 0.33. Inclusion of putative EA in the selection index instead of conception status resulted in 10 to 20% greater genetic gain for both fertility traits. In a genome-wide association study based on 1,200 dairy bulls with reliabilities >50% for abortion rate genotyped for 41,000 markers, 6 markers were found with nominal probabilities of <10-12 to reject the null hypothesis of no effect on EA rate. The markers with the lowest probabilities for EA rate were also included among the markers with the lowest probabilities for female fertility, but not vice versa. The marker explaining the most variance for abortion rate is located within the ABCA9 gene, which is found within an ATP-binding cassette (ABC) genes cluster. The ABC family is the major class of primary active transporters in the placenta.

Gene mapping and genomic prediction of bull fertility using sex chromosome markers

Service sire has been recognized as an important factor affecting dairy herd fertility. Our group has reported promising results on gene mapping and genomic prediction of dairy bull fertility using autosomal SNP markers. Little is known, however, about the genetic contribution of sex chromosomes, which are enriched in genes related to sexual development and reproduction. As such, the main goal of this study was to investigate the effect of SNP markers on X and Y chromosomes (BTAX and BTAY, respectively) on sire conception rate (SCR) in US Holstein bulls. The analysis included a total of 5,014 bulls with SCR records and genotypes for roughly 291k SNP located on the autosomes, 1.5k SNP located on the pseudoautosomal region (PAR), 13.7k BTAX-specific SNP, and 24 BTAY-specific SNP. We first performed genomic scans of the sex chromosomes, and then we evaluated the genomic prediction of SCR including BTAX SNP markers in the predictive models. Two markers located on PAR and 3 markers located on the X-specific region showed significant associations with sire fertility. Interestingly, these regions harbor genes, such as FAM9B, TBL1X, and PIH1D3, that are directly implicated in testosterone concentration, spermatogenesis, and sperm motility. On the other hand, BTAY showed very low genetic variability, and none of the segregating markers were associated with SCR. Notably, model predictive ability was largely improved by including BTAX markers. Indeed, the combination of autosomal with BTAX SNP delivered predictive correlations around 0.343, representing an increase in accuracy of about 7.5% compared with the standard whole autosomal genome approach. Overall, this study provides evidence of the importance of both PAR and X-specific regions in male fertility in dairy cattle. These findings may help to improve conception rates in dairy herds through accurate genome-guided decisions on bull fertility.

Enhanced pre-pubertal nutrition upregulates mitochondrial function in testes and sperm of post-pubertal Holstein bulls

Supplemental energy and protein during calf-hood (2–30 wk) in dairy bulls hastened puberty (~1 mo), upregulated steroid biosynthesis, concentrations of reproductive hormones and Sertoli cell maturation, with larger testes and greater sperm production (~25%) in mature bulls. The objective was to evaluate effects of feeding high (20.0% crude protein [CP], 67.9% total digestible nutrients [TDN]), control/medium (17.0% CP, 66.0% TDN) and low (12.2% CP, 62.9% TDN) diets from 2 to 30 wk on post-pubertal testes of Holstein bulls. Based on RNA sequencing, 497 and 2961 genes were differentially expressed (P < 0.1) in high- vs low- and high- vs medium-diet groups, respectively. According to KEGG analysis, oxidative phosphorylation and ribosome pathways were upregulated in high- vs medium- and low-diet groups, with majority of upregulated genes encoding for essential subunits of complex I, III, IV and V of OXYPHOS pathway. In addition, mitochondrial translation, mitotic nuclear division and cell division were enriched in high- vs medium-diet groups. Consistent with these results, a greater percentage of sperm from high-diet bulls were progressively motile and had normal mitochondrial function compared to medium-diet sperm (P < 0.1). Thus, enhanced early life nutrition upregulated mitochondrial function in testes and sperm of post-pubertal Holstein bulls.

Welfare implications for dairy bull calves

Abstract Dairy bull calves may experience compromised welfare as a result of production practices and management techniques implemented on farm. This includes high disease incidence due to poor ventilation, pain experienced as a by-product of processing procedures, social isolation, and hunger from inappropriate nutrition. Although dairy heifer calves may experience similar issues, these conditions are often exacerbated for dairy bull calves due to the low economic value of the individual animal. In addition, given the bull calf will likely not remain on the farm, this group of animals are more likely to receive less adequate care in the first weeks of life. Welfare issues such as increased rates of dystocia, failure of passive transport, dehorning, castration, and long transportation distances are all critical and will be discussed in this review. Therefore, the objectives of this article are to (1) evaluate current welfare concerns specific to dairy bull calves, (2) identify areas for improvement to mitigate poor welfare outcomes, and (3) review proper euthanasia techniques and protocols specific for calves. Ultimately there is still much to learn about specific areas for improvement relating to the welfare of dairy bull calves and future studies are needed. However, the industry should properly manage the welfare challenges of bull calves, identify opportunities within the industry to increase their value, and uphold our ethical responsibility to these animals.

Prevention of protein deficiency in dairy bull calves during fattening

The problem of low-quality protein in the diet of animals leads to excessive formation of a by-product (ammonia) in the rumen, which is not involved in the synthesis of microbial protein. The aim of the study is to develop a method for the prevention of protein deficiency in dairy bull calves. Bull calves of Kholmogorsk breed were grown in the vivarium of Institute under the controlled feeding and keeping conditions from 40 days of age to 14 months. Milk replacer feeding was carried out up to 70 days of age with free access to mixed feed and hay.In order to study the effect of concentrated feeds on metabolic processes and digestibility of nutrients, rumenal digestion factors were studied. It was found that physiological and biochemical parameters fit into reference values. The use of concentrated feed together with strict proportional administration of roughage during intensive growing and fattening of bull calves of dairy breeds makes it possible to reach an average daily increase of up to 1420 g by the age of 14 months and effectively pay for the feed with the productsupon the normal course of enzymatic processes in the rumen and throughout the body.

Public opinion and perception of rosé veal in the UK

Rosé veal is understood as meat from male purebred dairy calves. The UK veal market is limited, and calves are often killed at birth due to lack of purpose. A questionnaire, completed by 1002 respondents, investigated the UK public knowledge, perceptions and opinions of rosé veal, and whether raising awareness would sustain the rosé veal market. Most respondents (66%) did not eat rosé veal, mainly due to limited availability or exposure (31%) and animal welfare concerns (17%). A third of respondents knew the differences between rosé and white veal. After defining this, 61% of respondents would eat rosé veal, compared to 23% of respondents who ate it beforehand. Most respondents (91%) were willing to pay more for rosé veal burgers than the proposed average price for beef burgers. Increasing availability is key to encourage the sustainability of rosé veal production in the UK. These findings are useful for dairy farmers to strategically promote the use of purebred dairy bull calves.

Modelling effects of carcass weight, dietary concentrate and protein levels on the CH4 emission, N and P excretion of dairy bulls

Cattle farming is an important agricultural contributor to methane (CH4) emissions and has also a significant environmental impact through nutrient surpluses onto arable land. Therefore, the purpose of the present study was to model the effects of carcass weight (CW) and dietary concentrate and protein levels on the CH4 production and nitrogen (N) and phosphorus (P) excretion of dairy bulls fed grass silage-based diets. The modelling was based on treatment mean data from a growing cattle feeding experiment in which the concentrate and protein supply was manipulated. The three concentrate proportions were 300 (LC), 500 (MC) and 700 (HC) g/kg dry matter (DM) fed without (LP) or with (HP) rapeseed meal (RSM) supplementation. In the LP and HP diets the crude protein content of the concentrate was 128 and 160 g/kg DM, respectively. Methane emissions and faecal N output were predicted by the dynamic and mechanistic Karoline model. Manure P was calculated as P intake – Retained P. Predicted differences between the diets in CH4 emissions were small; the greatest difference was approximately 4% lower CH4 intensity expressed per kg carcass weight gain (CWG) in cattle fed HC diet compared with those fed LC or MC diets. Total N intake decreased with increasing diet concentrate proportion, which resulted in reduced urinary and faecal N output and reduced excretions per kg body weight (BW) and CWG. Increased N intake with RSM supplementation resulted in a greater total manure N output per day and per kg BW and CWG. Most of the increase in manure N output with RSM supplementation was urinary N. Manure P output per day and per kg BW and CWG increased with greater concentrate or protein supplementation. Within the practical range of grass silage-based beef cattle diets fed to dairy bulls the effects of diet composition on methane yield or intensity were small. However, taking into account carbon footprint of feed production, increasing proportion of grain in the diet can increase total carbon footprint. Emissions per unit of CWG markedly increase with increased CW. Manure N and P output and methane emission per unit of CWG increased more rapidly in BW above 570 kg, mainly because of reduced BW gain. Manure N and P output per kg CWG were mainly related to dietary concentrations of these nutrients and CW. Decreasing dietary N and P inputs is the best nutritional strategy to reduce manure N and P outputs.

224 Automatic image feature extraction for genetic analysis in cattle

Abstract Image analysis has increasingly become an important tool for increasing productivity in many industries, yet its application in breeding programs is under utilized. With coat color patterns from dairy bull images, we explore automatic image analysis that extracts features which can be used in genetic analysis. In order to remove the unnecessary background information, the current methods require time consuming human inspection. Here, we present and compare a composite method that creates a mask (i.e., removes the background portion of the image) and calculates the proportion of dark and light coloration in bulls (n = 657) from the breeds Holstein and Ayrshire in dynamic backgrounds (e.g., forest, grass, hay, snow, etc.). This composite method combines the supervised algorithm MASK-RCNN, an unsupervised image segmentation approach, and k-means color clustering. The first step identifies the region of interest removing the majority of the background noise, while the second and third steps optimize the identification of the bull and segments the color patterning. We find a very low discrepancy between the proportion of white and dark between the manual curation and the composite method (+/- 1.40%); with an immense reduction in data collection time. This automatic composite method greatly improves the efficiency of complex image segmentation and analysis without compromising the quality of the data extracted, making analysis computationally feasible for large data sets. The next step is to calculate genetic parameters from these extracted phenotypes with genomic and/or pedigree data.

Choice of artificial insemination beef bulls used to mate with female dairy cattle

Understanding the preferences of dairy cattle producers when selecting beef bulls for mating can help inform beef breeding programs as well as provide default parameters in mating advice systems. The objective of the present study was to characterize the genetic merit of beef artificial insemination (AI) bulls used in dairy herds, with particular reference to traits associated with both calving performance and carcass merit. The characteristics of the beef AI bulls used were compared with those of the dairy AI bulls used on the same farms. A total of 2,733,524 AI records from 928,437 females in 5,967 Irish dairy herds were used. Sire predicted transmitting ability (PTA) values and associated reliability values for calving performance and carcass traits based on national genetic evaluations from prior to the insemination were used. Fixed effects models were used to relate both genetic merit and the associated reliability of the dairy and beef bulls used on the farm with herd size, the extent of Holstein-Friesian × Jersey crossbreeding adopted by the herd, whether the herd used a technician insemination service or do-it-yourself, and the parity of the female mated. The mean direct calving difficulty PTA of the beef bulls used was 1.85 units higher than that of the dairy bulls but with over 3 times greater variability in the beef bulls. This 1.85 units equates biologically to an expectation of 1.85 more dystocia events per 100 dairy cows mated in the beef × dairy matings. The mean calving difficulty PTA of the dairy AI bulls used reduced with increasing herd size, whereas the mean calving difficulty PTA of the beef AI bulls used increased as herd size increased from 75 cows or fewer to 155 cows; the largest herds (>155 cows) used notably easier-calving beef bulls, albeit the calving difficulty PTA of the beef bulls was 3.33 units versus 1.67 units for the dairy bulls used in these herds. Although we found a general tendency for larger herds to use dairy AI bulls with lower reliability, this trend was not obvious in the beef AI bulls used. Irrespective of whether dairy or beef AI bulls were considered, herds that operated more extensive Holstein-Friesian × Jersey crossbreeding (i.e., more than 50% crossbred cows) used, on average, easier calving, shorter gestation-length bulls with lighter expected progeny carcasses of poorer conformation. Mean calving difficulty PTA of dairy bulls used increased from 1.39 in heifers to 1.79 in first-parity cows and to 1.82 in second-parity cows, remaining relatively constant thereafter. In contrast, the mean calving difficulty PTA of the beef bulls used increased consistently with cow parity. Results from the present study demonstrate a clear difference in the mean acceptable genetic merit of beef AI bulls relative to dairy AI bulls but also indicates that these acceptable limits vary by herd characteristics.

Prepubertal nutrition alters Leydig cell functional capacity and timing of puberty.

Leydig cell functional capacity reflects the numbers and differentiation status of the steroidogenic Leydig cells in the testes and becomes more or less fixed in early adulthood with the final establishment of the hypothalamo-pituitary-gonadal (HPG) axis after puberty. Factors influencing Leydig cell functional capacity and its role in puberty are poorly understood. Using a bovine model of dairy bulls fed four different nutritional regimes from 1 month to 12 months, and applying circulating Insulin-like peptide 3 (INSL3) as an accurate biomarker of Leydig cell functional capacity, showed that a high plane of nutrition in the first 6 months of life, but not later, significantly increased INSL3 in young adulthood. Moreover, INSL3 concentration at 4 months indicated a marked differential in early feeding regime and correlated well (negatively) with the timing of puberty, as reflected by the age in days for the first production of an ejaculate with >50 million sperm and >10% forward motility, as well as with testis size at 18 months. Reversing the diet at 6 months was unable to rectify the trend in either parameter, unlike for other parameters such as testosterone, body weight, and scrotal circumference. This study has shown that early prepubertal nutrition is a key factor in the development of Leydig cell functional capacity in early adulthood and appears to be a key driver in the dynamic progression of puberty.

Effects of soybean oil and dietary copper levels on nutrient digestion, ruminal fermentation, enzyme activity, microflora and microbial protein synthesis in dairy bulls

ABSTRACT The study evaluated the effects of soybean oil (SO) and dietary copper levels on nutrient digestion, ruminal fermentation, enzyme activity, microflora and microbial protein synthesis in dairy bulls. Eight Holstein rumen-cannulated bulls (14 ± 0.2 months of age and 326 ± 8.9 kg of body weight) were allocated into a replicated 4 × 4 Latin square design in a 2 × 2 factorial arrangement with factors being 0 or 40 g/kg dietary dry matter (DM) of SO and 0 or 7.68 mg/kg DM of Cu from copper sulphate (CS). The basal diet contained per kg DM 500 g of corn silage, 500 g of concentrate, 28 g of ether extract (EE) and 7.5 mg of Cu. The SO × CS interaction was significant (p < 0.05) for ruminal propionate proportion and acetate to propionate ratio. Dietary SO addition increased (p < 0.05) intake and total tract digestibility of EE but did not affect average daily gain (ADG) of bulls. Dietary CS addition did not affect nutrient intake but increased (p < 0.05) ADG and total tract digestibility of DM, organic matter, crude protein and neutral detergent fibre. Ruminal pH was not affected by treatments. Dietary SO addition did not affect ruminal total volatile fatty acids (VFA) concentration, decreased (p < 0.05) acetate proportion and ammonia N and increased (p < 0.05) propionate proportion. Dietary CS addition did not affect ammonia N, increased (p < 0.05) total VFA concentration and acetate proportion and decreased (p < 0.05) propionate proportion. Acetate to propionate ratio decreased (p < 0.05) with SO addition and increased (p < 0.05) with CS addition. Dietary SO addition decreased (p < 0.05) activity of carboxymethyl cellulase, cellobiase and xylanase as well as population of fungi, protozoa, methanogens, Ruminococcus albus and R. flavefaciens but increased (p < 0.05) α-amylase activity and population of Prevotella ruminicola and Ruminobacter amylophilus. Dietary CS addition increased (p < 0.05) activity of cellulolytic enzyme and protease as well as population of total bacteria, fungi, protozoa, methanogens, primary cellulolytic and proteolytic bacteria. Microbial protein synthesis was unchanged with SO addition but increased (p < 0.05) with CS addition. The results indicated that the addition of CS promoted nutrient digestion and ruminal fermentation by stimulating microbial growth and enzyme activity but did not relieve the negative effects of SO addition on ruminal fermentation in dairy bulls.

Bull efficiency using dairy genetic traits.

Dairy bulls are evaluated using progeny data and genomic testing to determine the quantity of specific traits that they will pass to their daughters. Some bulls excel in some traits but not others. Specifying these various traits as outputs, with the single input of insemination, technical, revenue, allocative, and profit efficiency of bulls available for artificial insemination are estimated using Free Disposal Hull. Although bulls generally are highly technically efficient, because only high performing bull semen is offered for sale, bulls are less revenue, allocative and profit efficient. These efficiencies are relative to peer bulls and can be updated as new bulls become available.

Different milk replacers alter growth performance and rumen bacterial diversity of dairy bull calves

The diets of calves predominantly comprise milk and the start of solid feed intake triggers a critical process in terms of the activity of the rumen microbiota and ruminal fermentation. However, little is known about alterations of the rumen bacterial diversity in dairy bull calves induced by milk replacers and other starters, such as solid pellets or hay. Thus, we analyzed the effects of partially replacing milk with pellets and Chinese wildrye in the diet on the growth performance and rumen bacterial composition in dairy bull calves. Thirty-two newborn Holstein bull calves were randomly allocated to four dietary treatments: group MFC was fed milk replacer, pellet diet, and Chinese wildrye; group MFR was fed milk replacer and Chinese wildrye; group MCO was fed milk replacer and pellet diet; and group MIL was fed milk replacer only. The diets were provided for 1 week before the trial and for 7 weeks in the experiment. At the end of the experiment, three calves from each treatment were slaughtered to determine the growth performance and slaughter traits, and the rumen bacteria composition was analyzed by 16S rRNA gene sequencing. The body weight, withers height, body length, and heart girth were higher (P < 0.05) in the MCO and MFC groups compared with the MIL and MFR group. In addition, the fresh weights of the liver, spleen, lung, kidney, rumen, reticulum, and abomasum were higher (P < 0.05) in the MCO and MFC groups. The sequencing results showed that at both the phylum and genus levels, the MIL and MFR groups clustered together, whereas the MCO and MFC groups clustered together. Bacteroidetes and Proteobacteria were more abundant in the MIL and MFR groups, whereas Firmicutes were more abundant in the MFC and MCO groups. The abundances of genera such as Dialister, Megasphaera, Acidaminococcus, and Mitsuokella were higher (P < 0.05) in the MCO and MFC groups. Our results showed that the growth performance of calves could be increased by feeding milk replacer with pellet diet, which may have been associated with changes in the diversity or abundances of rumen bacteria, especially bacteria from the phylum Firmicutes.

Growth curve of dairy artificial insemination bulls raised under Thai tropical conditions

Growth curve of dairy artificial insemination bulls raised under Thai tropical conditions

Genomic and phenotypic analyses of six offspring of a genome-edited hornless bull

Genome editing followed by reproductive cloning was previously used to produce two hornless dairy bulls. We crossed one genome-edited dairy bull, homozygous for the dominant PC Celtic POLLED allele, with horned cows (pp) and obtained six heterozygous (PCp) polled calves. The calves had no horns and were otherwise healthy and phenotypically unremarkable. We conducted whole-genome sequencing of all animals using an Illumina HiSeq4000 to achieve ~20× coverage. Bioinformatics analyses revealed the bull was a compound heterozygote, carrying one naturally occurring PC Celtic POLLED allele and an allele containing an additional introgression of the homology-directed repair donor plasmid along with the PC Celtic allele. These alleles segregated in the offspring of this bull, and inheritance of either allele produced polled calves. No other unintended genomic alterations were observed. These data can be used to inform conversations in the scientific community, with regulatory authorities and with the public around ‘intentional genomic alterations’ and future regulatory actions regarding genome-edited animals.

Characterization of antisperm antibody binding patterns in relation to sperm phenotypic attributes and field fertility in dairy bulls

To test our hypothesis that antisperm antibodies (ASA) might alter sperm phenotypic attributes thus leading to sub-fertility/infertility in bulls, ASA were generated in crossbred male calves by immunizing with sperm two times. Cryopreserved spermatozoa from crossbred bulls (n = 24) with different field fertility ratings were incubated with ASA and different patterns of ASA immunolocalization were studied. In addition, sperm membrane integrity, acrosomal integrity and cryo-capacitation status were also assessed. Immunolocalization of sperm antigens using antisperm antibody revealed three major patterns (Acrosomal-AR, apical-AP and, acrosome and tail-AT). The proportion of ASA reactive spermatozoa was significantly (P < 0.05) higher in low- and medium-fertile bulls compared to high-fertile bulls. Among the three patterns, the proportion of spermatozoa with AR pattern was significantly (P < 0.05) higher in low- and medium-fertile bulls compared to high-fertile bulls. The proportion of membrane and acrosome intact spermatozoa was significantly (P < 0.05) higher in high-fertile bulls compared to medium- and low-fertile bulls. There were no significant differences in the proportion of cryo-capacitated spermatozoa among high-, medium- and low-fertile bulls. The relationship between ASA reactive spermatozoa and conception rates (CR) of bulls was highly (P < 0.01) significant and negative. Similarly, AR and AT pattern were also significantly (P < 0.01) and negatively related to CR of bulls. The reactivity of spermatozoa with ASA was also significantly (P < 0.01) and negatively related to the membrane and acrosome integrity of spermatozoa. It was concluded that the proportion of spermatozoa responding to ASA was higher in low-compared to high-fertile bulls and ASA localization in sperm acrosomal area was negatively related to sperm membrane and acrosomal integrity and bull fertility.

Exposing dairy bulls to high temperature-humidity index during spermatogenesis compromises subsequent embryo development in vitro

The possible impact of natural heat stress on animal fertility is currently a major concern for breeding companies. Here, we aimed to address this concern by determining the effects of natural heat stress on the fertility of Holstein bulls located in the Netherlands. Semen samples were collected from six bulls at two locations in March 2016 (low temperature-humidity index (THI) group; maximum THI of 51.8 and 55 at their respective locations) or August (high THI group; maximum THI of 77.9 and 80.5 during meiotic and spermiogenic stages of spermatogenesis, 42 to 14 days prior to semen collection). The effect of heat stress on semen quality was assessed by sperm morphology, motility, reactive oxygen species production, lipid peroxidation, viability, and DNA fragmentation. Moreover, we evaluated the development of embryos generated in vitro by low and high THI semen, and determined inner cell mass/trophectoderm ratio, apoptotic cell ratio, and embryonic gene expression in day-8 blastocysts. An increase in cell death (propidium iodide-positive cells; P = 0.039) was observed in the high THI group (31.5%) compared to the low THI group (27.6%). Moreover, a decrease (P < 0.001) was observed in the total blastocyst rates at day 7 post-insemination (15.3 vs 20.9%) and day 8 (23.2 vs 29.6%) in the high THI compared to the low THI group, respectively. There were no differences in the relative abundance of candidate transcripts examined. In conclusion, sperm samples from dairy bulls obtained during a period with higher THI had reduced viability and led to a decrease in blastocyst development and delayed hatching, compared to semen collected during a period with low THI.

Effects of pantothenic acid and folic acid supplementation on total tract digestibility coefficient, ruminal fermentation, microbial enzyme activity, microflora and urinary purine derivatives in dairy bulls

AbstractThe effects of pantothenic acid (PA) and folic acid (FA) addition on digestibility coefficient, ruminal fermentation and urinary purine derivative (PD) excretion in dairy bulls were evaluated. Eight rumen-cannulated Holstein dairy bulls were allocated to a replicated 4 × 4 Latin square design according to a 2 × 2 factorial arrangement. Diets were supplemented with two levels of FA (0 or 8.0 mg/kg dietary dry matter [DM]) and two of PA (0 or 60 mg/kg DM). The PA × FA interaction was not significant for all variables. Both supplements increased DM intake and average daily gain, but decreased a feed conversion ratio. Digestibility of DM, organic matter, crude protein and neutral detergent fibre increased, but ether extract digestibility was unchanged for both supplements. Digestibility of acid detergent fibre only increased with FA supplementation. For both supplements, ruminal pH and ammonia nitrogen (N) decreased, but total volatile fatty acid (VFA) concentration increased. Acetate proportion only increased with FA supplementation. Propionate proportion decreased for both supplements. Consequently, the acetate to propionate ratio increased. For both supplements, activity of xylanase and pectinase, population of Ruminococcus albus, R. flavefaciens, Fibrobacter succinogenes and Ruminobacter amylophilus and total PD excretion increased. Additionally, activity of carboxymethylcellulase, cellobiase, α-amylase and protease, and population of total bacteria, fungi, protozoa, methanogens, Butyrivibrio fibrisolvens and Prevotella ruminicola increased with FA addition. The results suggested that PA and FA supplementation stimulated ruminal microbial growth and enzyme activity, resulting in an increased digestibility coefficient and ruminal total VFA concentration in dairy bulls.